stone wall renovation

[Gherk]

Looking for the best solution to the renovation/retaining of an existing stone wall. Wall was built 1880's. Is the perimiter wall to a varandah spanning 6.3 meters with 90deg corner (span 1) then another 6 m (span 2)both spans are tied together at the corner. Span 1 height starts at 0.9m increasing to 1.5m at corner then span 2 constant at 1.5m. Wall is adjucent to main wall of house then runs parallel with main wall of house but not tied to main wall of house. Wall has backfill between it and main house wall of a sandyloam then stone rubble above then a concrete floor was layed within the walls over the top. Due to aging, cracking of concrete and subseqient ingress of moisture and suspected swelling of backfill wall has bowed & cracked at several points. All concrete and backfill has been removed and i want to straighten, secure, tie, both spans of wall ready for new varandah to be built within,looking for suggesstions of best method, demolition and rebuild of wall not an option. Also what would be most desirable backfill to go full height of wall then have concrete layed over top? Thanks and gratitude in advance.